He played college football for the Washington Huskies, and was selected by the Cardinals in the second round of the 2017 NFL draft.

He participated at Washington's Pro Day and only ran positional drills for over 50 NFL team representatives and scouts.

[24] Due to NFL's rules for colleges who follow quarters systems, Baker was unable to attend organized team activities or minicamp until the University of Washington's graduation day.

[25] He impressed coaches throughout training camp and was named the backup free safety to Tyrann Mathieu to begin the regular season.

[27] On November 19, 2017, Baker earned his first career start after Tyvon Branch suffered a torn ACL the previous week.

[29][30] In Week 16, he tied his season-high of 13 combined tackles (eight solo) and broke up a pass in the Cardinals' 23–0 victory against the New York Giants.

[36] On January 22, 2018, the Cardinals announced their decision to hire Carolina Panthers' defensive coordinator Steve Wilks as their new head coach.

[39] In Week 5, Baker collected a season-high 16 combined tackles (11 solo), deflected a pass, and made a sack during a 28–18 win at the San Francisco 49ers.

[44] In week 10 against the Tampa Bay Buccaneers, Baker recorded a team high nine tackles and forced a fumble on running back Ronald Jones II which he recovered in the 30–27 loss.

[45] In the 2019 season, Baker finished with a half-sack, 147 total tackles (104 solo), six passes defended, and one forced fumble in 16 games and starts.

[49] On August 25, 2020, Baker signed a four-year, $59 million extension with the Cardinals, making him the highest-paid safety in NFL history at the time.

[52] On Monday Night Football in Week 6 against the Dallas Cowboys, Baker forced a fumble on running back Ezekiel Elliott that was recovered by the Cardinals, sacked quarterback Andy Dalton once, and recorded his first career interception off a pass thrown by Dalton during the 38–10 win.

[55] Baker was named the NFC Defensive Player of the Month for October after tallying 31 tackles, two sacks, two interceptions, and a forced fumble.

[57][58] In the 2020 season, Baker finished with two sacks, 118 total tackles, two interceptions, six passes defended, and one forced fumble in 15 appearances and starts.